Your kitchen sounds lovely! If you go with white chairs I'd be tempted to use a darker wood for the table, similar to the color of your walnut floors. That way you'll have a nice contrast between chairs and table that echoes the contrast between cabinets and floors. But you could also use a lighter wood, or an antique farmhouse table made of pine or cherry, with either white or black chairs. Or you could have a table with white legs and a wood surface. Your black and white kitchen will go well with many combinations.